Hydroxybenzophenones have been known in the art for quite sometime, particularly with respect to their utility as stabilizers for organic polymers. More particularly substituted and unsubstituted 2-hydroxybenzophenones have been widely used as UV stabilizers for polyolefins. Thus they are of significant commercial interest. The manufacture of substituted and unsubstituted 2-hydroxybenzophenones, particularly by commercial processes, yields products which very often contain impurities. These impurities contribute color to the product and/or cause the product to be color unstable upon standing, particularly when exposed to light and air. Color changes and/or darkening sometimes occur in a matter of a few hours at room temperature. Such color changes, which are often caused by a small percentage of impurity which is difficult to remove, reduce the commercial acceptance of such substituted or unsubstituted 2-hydroxybenzophenones and thereby impedes the commercial use of these materials. To, at least in part, overcome these color and color instability problems the prior art resorted to physical means to highly purify the impure substituted and unsubstituted hydroxybenzophenones. These physical means have added steps and cost to the preparation of the 2-hydroxybenzophenones and in some cases caused decreased yields.
Since hydroxybenzophenones are valuable UV stabilizers in commerce, it is highly desirable to overcome these color and color instability problems, particularly without burdening the process and significantly increasing the cost of making them.